Thanks to a few scientists who dedicated their time to discover facts about the atom, we now know that they look kind of insane and are more than just an orb, but contain more particles than many think. The first person to mention the existence of such particles was Democritus who lived circa 400 BCE. Though he mention atoms, he had no experimental evidence and was more of a philosophical scientist rather than a proof scientist.
Roger Bacon created the basis that science should be backed up with experimental evidence in the thirteenth century.
The Law of Conservation of Mass was proposed by Antoine Lavoisier in 1774 which stated that in chemical reactions mass in neither created nor destroyed.
Joseph Proust established the Law of Constant Composition. This law states that each pure chemical compound always has the same percentage composition of each element by mass.
The Atomic Theory was put into terms by John Dalton in 1803-1808 which listed a few things:
- All matter is composed of tiny, indivisible particles, called atoms, that cannot be destroyed or created.
- Each element has atoms that are identical to each other in all of their properties, and these properties are different from all other elements.
- Chemical reactions are simple rearrangements of atoms from one combination to another in small whole number ratios.
Also the Law of Multiple Proportions was established by Dalton. He said when two elements can be combined to make two different compounds, and if the samples of these two compounds was taken so that the masses of one of the elements in the two compounds are the same in both samples, then the ratio of the masses of the other element in these compounds will be a ratio of small whole numbers.
Michael Faraday proved that electric current could cause chemical reactions to occur. Big whoop. I mean, MOVING ON!
Sir William Crookes developed the cathode ray. With the aide of this silly looking device, a glow was noticed between two electrodes when a high voltage was applied to them. The stream of what we discovered were electrons could be deflected by a magnet and the stream could be changed if an object was placed in the path.
J.J. Thomson discovered electron with the cathode ray. The mass to charge ratio was established by Thomson as well. It is m/e = -1.76 * 108 coulombs/gram-1 . He discovered, too, that the mass of a single electron is 1.76 * 10-28 gram.
Robert Millikan did his oil drop experiment and found the charge of a single electron to be -1.60 * 10-19 coulomb.
The alpha and beta particles were found by Ernest Rutherford. With Hans Geiger and Ernest Marsden, he performed the gold foil experiment and appointed the nuclear model of the atom which was explained as a small, dense, and positively charged nucleus surrounded by empty space sparsely occupied by electrons. Rutherford also found the proton, which is the particle that has a positive charge. He found it to have a mass of 1.67 * 10-24 gram which is 1,836 times heavier than the electron.
The neutron was discovered by an English Physicist named James Chadwick. It has almost the same mass of a proton and has no charge and therefore is neutral.
Niels Bohr created the shell model of the atom. He assumed that electrons orbit the nucleus in certain set orbits. Max Planck helped Bohr’s model out by describing light as packets, or quanta of energy called photons.
Louis de Broglie (de bròj lee ay) believed that electrons could display some wave-like properties if light can be considered as particles.
The wave-mechanical theory – determined that the electron in the model is described by a probability of where it will be located – was established by Erwin Schrödinger.
The uncertainty principle was developed by Werner Heisenberg in the 1920s. It states that the position and the velocity of a particle cannot be known at the same time. As one becomes more known, the other becomes less certain.
That will be all I have for the atom for the present. More data will be added soon when I study more of it.
